<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
        "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
    <title>Title</title>
    <!--CSS的引入方式共有三种：行内样式、内部样式表、外部样式表-->
    <!--内部样式表-->
    <style type="text/css">
        div {
            background-color: royalblue;
            width: 400px;
            height: 300px;
        }
    </style>
    <style type="text/css">
        div{
            background-color: royalblue;
            width: 400px;
            height: 300px;
        }
    </style>
</head>
<body>
<div style=""></div>
<div style="width: 400px;height: 300px;background-color: #EEEEEE"></div>
<div style="width: 400px;height: 300px;background-color: #EEEEEE"></div>
<div style="width: 400px;height: 300px;background-color: #EEEEEE"></div>
</body>
</html>